Radio Frequency (RF) transceivers may use quadrature modulation for higher spectral efficiency. The quality and accuracy of the quadrature signals that are used for modulation and demodulation directly affect the performance of the transceiver, and thus it is desirable that the quadrature signals be precise and have a low phase-noise. Consequently, these signals may be generated locally at the transceiver.
Generating precise, high-quality, low phase-noise quadrature signals with a phase-shift of π/2 may be very difficult. In some conventional oscillators, two resonant tanks are used, such that each tank operates in a non-linear region of its phase/frequency characteristic. This may result in degradation in the overall quality factor of each tank, reduction in output amplitude, and reduction in the phase-noise performance of the oscillator.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.